1. Field of the Invention
The present invention relates to a photovoltaic cell product and a method for its manufacture.
2. Description of Related Art
Photovoltaic devices or solar cells absorb sunlight and convert it directly into electrical energy. The basic scientific principles which underly the effect of converting light energy into internal voltages using photovoltaic cells are well understood.
Most types of photovoltaic cells have a photoactive area, i.e., an area that generates electricity in response to light and is composed of a semiconductor layer disposed between two electrode layers deposited on a flat, supporting substrate. The photoactive area is divided into a number of photovoltaic cells interconnected in series to boost the voltage output. The photovoltaic cells may then be encapsulated, e.g. with plastic, to protect the cells from the external environment during transportation and operation of the cells. A number of electrically interconnected photovoltaic cells may be supported on a common rigid medium, such as glass, to form a photovoltaic module.
The process of sequentially forming photovoltaic layers onto a supporting substrate is a common technique for making "thin film photovoltaic cells," also a well known product. Most thin film solar cells are deposited onto glass as part of the manufacturing process. However, the sequential deposition of layers on a rigid medium such as glass is expensive, cumbersome, not well suited to high speed operation, and often expensive to ship. Moreover, the plastic casing is expensive and it remains a failure point throughout the life of the photovoltaic cells due to the tendency of plastic to degrade in sunlight. Thus, there is a need for an improved process of making thin film cells which is more suitable for high volume production, increased life span, versatility of the product, and lower manufacturing and transport costs.
U.S. Pat. No. 5,674,325 issued to Albright et al. on Oct. 7, 1997 is an example of a method of manufacturing a thin film photovoltaic device. Albright et. al. describes a process involving a "surrogate substrate" that is separated from film layers so that the film layers may eventually be incorporated into a photovoltaic cell to be supported on a permanent substrate. The Albright device does not have a permanent substrate onto which the photovoltaic material is deposited, rather it has a surrogate substrate. More importantly, the Albright device does not contain or suggest the use of a contact transfer release sheet as a top layer, over the thin film cells, or elsewhere. The same holds true for U.S. Pat. No. 5,868,869 issued to Albright et al. on Feb. 9, 1999. Other methods and devices similar to, or analogous with, thin film cells and their manufacture include U.S. Pat. No. 5,520,763 issued to Johnstone on May 28, 1996, which describes a manufacturing process in the printing art that uses a foil strip and a release sheet fed through a roller. Johnstone does not suggest the present method of making a photovoltaic device. U.S. Pat. No. 5,417,770 issued to Saitoh et al. on May 23, 1995 is a forming method used in the manufacture of a photovoltaic device. Saitoh et al. do not suggest the present method of making a photovoltaic device. U.S. Pat. No. 3,729,343 issued to R. D. Thomas on Apr. 24, 1973 describes a method of rolling a thermocouple tape. R. D. Thomas does not suggest the present method of making a photovoltaic device.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.